設帳篷為X頂
4 * X + 16 = 6 * (X - 2) + 4 * 2
4X + 16 = 6X - 12 + 8
4X + 16 = 6X - 4
2X = 20
X = 10
總人數為 4 * 10 + 16 = 56
答:56人